Drilling mud containing a telomer



r r 2,911,365 DRILLING MUD CONTAINING ATELQMER at. D. Burland and RobertG. Roth, La Marque,Te1 r., 'assignors to Monsanto Chemical Company, St.Louis, Mo., a corporation of Delaware No Drawing. ApplicationApril 4,1955 v Serial No. 499,242 l 8 Claims. (Cl. 252-85) This inventionrelatesto aqueous dispersions of finely divided solid materials.'Mor'e'particularly this invention relates:-'to"the use'-;of telomers ofacrylic acid,'its salts and acrylaniide"," as'dispersing agents forfinely divided solid materials in an aqueous medium.

This application is a continuation in part of application Serial No.470,514, filed November 22, 1954, and application Serial No. 451,074,filed August 19', 1954, both now abandoned.

Many'appliiiations reqilirethe suspension or dispersion of finelydividejd solid materials in anlaqueous medium. Insuch applic 'ons, it'isc'ustomary to add dispersants to the composition. Dispersantsfacilitate the prepare? tionof a uniform or homogeneous dispersion ofthe finely Satisfactory dispersants must not only accomplish this "nitedStates Patent clays to be used jof aqueous-dispersions of pigments I ofpigment suspended in It is a particular object of this invention toprovide 1 improved aqueous dispersions of finely divided pigments.

It is also an object of this invention to provide improved aqueousdispersions or suspensions of; lays having particular utility indrilling muds.

It is another object of this invention to provide a method ofcontrolling the viscosity of aqueous drilling muds without adverselyaffecting other properties such as gel strength and, filtr'jation rate.

A still further objectof the invention is to provide an aqueous drillingfluid having controlled viscosity;

Other objects will become tion of the. invention. 7

It has now been discovered that significantly improved aqueousdispersions of finelyi divided solid materials can be prepared by;incorporating therein aminor amount of a telomer; of acrylic acid, itsalkali metalor ammonium salts, or acrylamide and a halogenated alkane,said tel:

omers containing the monomeric. unit having-the formula wherein Y may beNH OH or OM, M being a cation selected from the group consisting of thealkali metals or ammonium and n is an integer from 2 to 30. Forconvenience, hereinafter these telomers are referred: to as acrylictelomers. LParticularlyuseful aqueous dispersions of finely dividedsolid materials can be prepared by in- ..solids concentration apparentfrom the descrip 2 V corporating therein a minor amount of an acrylictelomer having the formula 1 f i Y I V wherein Xmay be hydrogen or ahalogen, Y 1:nay be.

NH OH, or OM, M being a cation such as' an alkali metal or ammonium, Zis a halogen, n is an integer from useful in the preparation ofaqueousdispersions ofpig preparation. of aqueous dispersions of;-

ments and in the as drilling muds.

In the manufacture of paints, practically all pigments employed,particularly inorganic pigments, are prepared or processed in .aqueousmediaand are initially recovered as a pulp or paste. In the preparationof aqueous pigment pulps themselves as well as in the dry grinding ofpigments intended for water dispersion, surface active agents are oftenused to improve the degree of'dispersion. The degree of dispersion ofthe pigment has a strong influence on the rheological properties of thepaint' as well as upon its; covering power. 'Materials used in the priorartfor dispersing pigments have been many and varied and havein'cluded,for example, naphthalene sul fonates, proteins, lignin s 'u1fonates,'fatty alkyl sulfates and quaternary ammonium compounds. It hasnow been discovered that acrylic telomers are particularly effectivedispersing agents for pigmentsufThe acrylic telomers are characterizedas products which, by their presence. act to prevent flocculation oragglomeration ofso'lid particles water. ;In contrast tothe LCOIl'lfpounds so employed in-the'priorart, smaller amounts of the acrylictelomers are required to promote acom parable degree of dispersion inpigments, .With most dispersantsffurther addition after maximum thinninghas.

been attained is characterized by'an immediate increase" in viscosityf'This is not the case, however, with the thinners-of the presentinvention since maximum thin ning is maintained over a wider range ofdispersant con-f centration and the likelihood of overtreatment is,therefore, minimized. The latter are those of the prior art for-thereason that they maintain a constant low level of viscosity over a muchwider solids concentration range. They thus have the advantage ofpermitting the preparation of suspensions of much higher per givenquantity of dispersing 1 agent.

In accordance with the invention, the dispersion of a pigment,particularly an inorganic pigment, suspended in an aqueous medium may bereadily effected by incorporating in said suspension a small quantity ofan acrylic telomer. Consequently, the invention is also considered asencompassing a composition of matter which isa mix- 'ture comprising afinely-divided pigment suspended in an aqueous vehicle and a telomer tomaintain the sired level.

The aorylic-"teleorner dispersin agents of the invention are effectivegenerally with all pigments. Of the many in existence which canbedispersed in aqueous medium using the thinning agents described hereinare ferric oxide,"ironbluesQjred lead, white lead (basic'carbonate),white lead (basic sulfate), lead chr'omate, zincoxide, zinc-'chromate,zinc sulfide, lithopone, chromium oxide, dioxide (anatase), titaniumdioxide antimony oxide, cadmium sulfide, lead titanate,

suflicient amount of an' a'crylic viscosity of the mixture at a de-Patented Nov. 3, 1959 I also more desirable than v and the like. Theyare also useful with extended pigments such as titanium-barium,titanium-calcium, titanium-magnesium, zinc sulfide-barium, zincsulfide-calcium, and zinc sulfide-magnesium pigments orv with anycombinations of'pigments used to provide pigments ofother than theprimary colors such as lead chromate-lead oxide for making lightershadesof chrome orange, and iron blue and lead chromate for making chromegreens.

The quantity of dispersing agent to be useddepends, of course, onthedegree of dispersion desired or, in other words, the consistency orticle size of the dispersate, and the concentration of the dispersion.In general, from 0.05% to by weight of the dispersing.agents of theinvention based. on the dispersate will give good results. Thisappliestoall typeszof dispersates, whether or. not they. be pigments.The acrylic telomer dispersing .agentmay be added to the pigmentsuspension as an. aqueous solution or as a solid'in powdered form or itmay be incorporated as solid. with the dry. pigment in the grinding ormilling operation Alternatively, thedispersion and-mixing may take placesimultaneously by intimately mixing the pigment with water and thedispersing agent.

The invention is illustratedin the following examples but these are notto be construed. as limiting it in any manner except as it is limited inthe -appended claims. Viscosimetric measurements have been employed forevaluatingdispersing'action. The viscosity of the system is measuredandjth'e. fluidity of the sample is taken as an indication of therelative degree of dispersionbased on the commonly accepted conceptionthat for the same concentration of solids under similar conditions, themore fluid is the sample, the more completely dispersed are thesuspended particles. The Stormer viscosimeter was employed in obtainingthe data given here.

EXAMPLE 1 A. 50% suspension of pigment-grade iron oxide (Mapico Red No.S67-Ribelin Co., Houston, Texas) in water was prepared by stirring. 150grams of the pigment in "150 grams of water at high-speed for 5 minutesin a standard mixerQ The viscosity of the suspension was measured. Smallincrements of a aqueous solution of the sodium salt of a teleomer ofacrylic acid and. carbon tetrachloride in which the acid telomer had amolecular weight of 1490 were then. added with oneminute stirring aftereach addition. Viscosity measurements were made after each addition ofthe dispersing agent. The data presented in Table I below illustrate theeffectiveness of the teleomer as a dispersing; agent.

Table 1 Cone. of Viscosity at' Dispersant 600 r.p.n'1. TelomerDispersant Added (g.) (Wt. Percent Stormer of Pigment) (cps) EXAMPLE 2The experiment of Example 1 was repeated on a fresh 50% iron oxidesuspension with the exception that a 10% fluidity desired, the paraTable 11 Cone. of Dis- Viscosity at Lignosulfonate Dispersant Added (g.)persant, W t. 600 r.p.m.

Percent of Stormer- Pigment (cps) A comparison of these datademonstrates that the acrylic acid telomers of the invention are suchgood dispersing agents for inorganic pigments, thatjthey: are

actually superior to a representative dispersing agent less ofthetelomer beingrequired to achieve optimum fluidity in the system.

EXAMPLE 3 the pigment in g. of water respectively at high speed forfive'minutesin a standardmixer. I I" Incremental quantities of theacrylic acid telomer em ployedin Example 1 were added to one of thesamples with onetminute stirring after additions and: viscositymeasurements were made after each addition. The same, procedure wasfollowed with the second sample. except thata representative sodiumlignosulfonate commercial dispersingagent was employed as the thinning.agent The data obtained are, presented in Table III below.

Table III Sample No. 1 Sample No. 2

3 Cone. of Viscosity Lignosul- Cone. of Viscosity 'lelomer Dispersat 600fonate Dispers at 600 Dispersnnt' ant, Wt. rpm. Dlspersant ant,Wt;r.p.1n. added (g) percent of Stormor Ad e percent 01- Stormer Pigment(cps) (g.) Pigment (cps) 0 0 300 '0. 0 0.0 800 0.100 56 O. 16 0. 106 3000.133 11 0.20 v 0.133 150 0.200 11 01325 0.210 66- 0. 268 11 01 105. 0;270 '41 0. 333 11 0.525 0.350 14 0. 400 11 0. 705 0. 510 14 0. 533 111.705 1.175 10' 0. 665 l1 The effectiveness of the telomere of-theinvention as dispersing agents for pigments isevident from the abovedata; Maximum thinning of the zinc oxide suspension'is obtained withonly 0.13 percent (basedon the pig- -ment) ofthe acrylic acid telomersas compared to the EXAMPLE 4 The experiment of Example '3 was repeatedin every detail but with pigment-grade titanium oxide (Titanox from theTitanium Pigment Corp.,,South Amboy,"

NJ); Results are tabulatedbelow in Table IV.

Table IV Sample No. 1 Sample No. 2

Cone. of Viscosity Lignosul- Cone. of Viscosity Telomer' Dlspersat 600tonate Dlspersat 600 Dlspersant ant, Wt. r.p.m. Dispersant ant, Wt.r.p.m. Added, (g.) percent of Stormer Added percent of Stormer Pigment(cps) (g.) Pigment (cps) -Here again, as with the zinc oxide, thethinning agents of the invention are five or six times morelefiectivethan the commercial thinner at maximum thinning value. Much less. of thetelom er jdispersing agent is required to produce a comparable, degreeof dispersion.

' EXAMPLE In order to further demonstrate the efliciency of acrylictelomers as dispersing agents, the highest solids content slurry thatcould be obtained using the maximum concentration ofdispersingagenfshown for the titanium dioxide suspensions in Example 4.This was done by adding incremental quantities of 10. grams of thepowdered pigment to the 50% suspensions containing the maximumconcentration of both the telomer. dispersant (0.266%) and the sodiumlignosulfonate dispersant (0.36%), stirring thesefor one minute at highspeed and measuring the viscosity of the resulting slurries. Resultsobtained. are tabulated below in Table V.

. I y (we) These data demonstrate conclusively that the dispersingagents of the invention are highly eflective and make possible thepreparation of dispersions with high solids content andlow viscosity.Further, they supply evidence of their superior-ity'overotherrepresentative agents in theart.

While the preceding Examples 1-5 have illustrated the use of the sodiumsalt of a telomer of acrylic acid and carbon tetrachloride, comparableresults are obtained if this telomer is replaced with the sodium salt ofa telomer of acrylic acid and chloroform or dichloromethane. In anotherspecific embodiment of this invention, acrylic telomers are used toprepare drilling muds having exceptional properties. v

Drilling of an oil or gas well by the rotary method is performed byrotating a bit attached to the end of a hollow drill pipe, knownas adrill stem, which-extends downward through thejwell bore. As the drillstem is rotated from the surface, the bit cuts or grinds away theformation into smatl fnagments known as cuttings which W Percent)thedrill stem and the walls of the borehole to the surface of the earth.In addition 'to the function of pickingup the cuttings produced by thedrill bitand carrying them to the surface, the drilling mud serves anumber of other purposes. It must lubricate and cool the drill stem andbit; it must apply a-hydrostatic pressure to the formation tocounterbalance the pressure 'of'any' liquids or gases which may "beencountered in the various strata penetrated by the drill bit in orderto prevent flow of formation fluid into the borehole;',and it must formon the Walls of the borehole a thin impervious'layer-or sheath of solidmaterial which serves to reduce loss of water from the borehole to theformation and provides support for the walls to prevent-their collapseinto the drilling" hole. i

Y The ability of any given mud. to carry-out these iimportant functionsdepends upon certainsreadily measurable physical properties- Viscosityisan important characteristic. The drilling mud must have a viscositysufliciently high to permit it to elfectively suspendand remove thecuttings from the bottom of the well. On the other hand, the viscositymust at'thesame time be low :enough sothat the mud may bereadily-circulated at the'desired rates Without requiring excessive pump'pressu'resxand/or power consumption. .j v -:-.i The properties of thedrilling-mud are-changed during drilling because some of thestratatraversed are com posed of shales, clays, etc., whichbecome dispersed inthe fluid and produce a gradual increase in the viscosity of thedrilling mud with continued use. Contamination by salt brines or as aresult of cementing operations likewise causes undesirable increases inviscosity. The custom of using weighting materials, such as barytes orhematite, to increase the density of the mud also results in increasedviscosity. If the viscosity is allowed to -become too great,difliculties are encountered both in pumping the mud and in removingcuttings from the a mud at the surface. Another serious problem withhighly viscous fluids is that of gas cutting. The gas from the formation.or-formations through which the j well passes becomes entrained in thedrilling fluid since must be removed from the hole in order that thedrilling may progress. To carryfaway these cuttings, a fluid com- Q' Imonly referred to down the drill stem, self, and then upward through theannular space between .of course, be any finely Y vehicle. as drilling.mud is continuously pumped through channels in the drill bit ititcannotireadily escape in the surface pits and the fluid which isrecirculated consequently has a lighter weight than is desired. Thisgreatly lessens its efliectivenessin holding 'back formation pressuresand significantly increases the possibilities of a blowout. I For these,reasons, it is obvious that the consistency of the drilling mud must becarefully controlled. l I In practice, reduction. in' viscosity maybeyachieved by dilutionwith water or by the addition of dispersants. Theformer method, while it may be satisfactory in specific instances, hasmany drawbacks anddisadvantages and so thepractice of. adding variouschemicals to drill ing fluids-to reduce viscosity has. become more orless standard] A large number of .chemicalssuchas pyrophosphates,polyphosphates, tannates, humates, and phytates have been employed inthe prior art. In many. cases, however, .the extentto which a drillingfluid; can be controlled by such chemicals is limited. 7 i v V Inaccordance With the invention, the viscosity of an aqueous drillingfluid may be controlled efiiciently by incorporating therein asuflicient amount of an acrylic telomer. The composition of theinvention may be de scribed briefly as a mixture comprising finelydivided solid material, an aqueous vehicle in which the solid materialis dispersed or suspended, and a sufiicient amount of an acrylic telomerto maintain the viscosity of the fluid at the desired level.

material of the invention may,

The finely divided solid divided solid which is capable ofbeingdispersed or suspended in an aqueous liquid Ordinarily, such materialwill include hydrat able clay or colloidal clay bodies such as Wyomingbentonite', commercial medium-yield drilling clays mined in variousparts of the country such as in Texas, Ten

"7 Loui iana-and fliosqproduced when clayey subsuifaceif nnations aredril ed; Weig t m t adde it increase specific gravity suchasbarytes,iron exide,-. alci mcarbonate, silica-san ytheli e may als be EXAMLE 6 15 aquegus jmedium. mayl.be fresh water suchas is A synthetic dnllmg mudwas prepared containmg 35% l f li fl k .f be salt Water solids suspendedin water. On a dry basis, the solids fm'mihe,geagox.,fmm.wflxlitrmayfiven include m consisted of l0 parts by welght of Tennessee ball clay,watencmulsion, a. water which has *becomeeontamb 1 Pa Welght of Bentfmteand fi'P -f mated infzsomeiwmyzywim:sman quantities of .oil to Dlx ebond clay. The breakover from sodium-base which jsiugh hi1 has be addedin gain ,Some desired to. lime-base fluid was achievedby adding 5 g. ofhydrated advamagg' lime for each 350 cc. of the suspension and varyingiriscontemplatedthanthe drilling muds of th i amounts of an acrylictelomer. Mud samples were made tion may ailsocontainzothersadditives.besides the acrylic With two different p s of acrylic ltelomers,stelomers of the invention. Materials such as caustic; Rated 111 and thefollowlflg ex911119165 as u b h li ggment gypsum d h lik may b No. 1 andTelomer'No. 2, WhlCh were the sodlum salts added -10 the -.dri1ling mudt the. urfa or may b of telomers of acrylic acid and carbontetrachloride in encountered in subsurface formations during drillingwhich the acid telomers'had molecular weights of 1250 op ti s, and 1890,respectively. The-addition of caustic usually *Thequantitiesof: theacrylietelomers 'to be employed required in breakover was obviated inthis case bythe in :the idrilling mud .ofthe invention will vary withcirbasic nature of the telomer thinner. The samples were cumstances overa'reasonably wide range and the amount 7 then tested by means ofthe-standard procedures given employed in aspecific sus'pension ordispersion will .de in TRecommended Practice for StandardField Procedurepend-on :these circumstances and the characteristics of for TestingDrillingFluids" of the Americanfetroleum the material treated.Ordinarily, satisfactory'results will Institute, third edition, May1950, toevaluate the effect he obtained with quantitiesranging'from 1 to4 pounds of the telomers as thinners. Results ofthese tests are ofatheacrylic telomer per 42-gallon barrel of drilling presented in Table VI.Table VI Lb. Viscosity at Gel'strength Filtration rate, Additiveadditive 600r.p.m. cc.inmin. pH

- per bbl. Stormer, A.P.I.

cps.

0 Plastic (5 mln.) 10.5 0.5 .do. 40(3mir1 12.2 1.0 79 (13min) 12.0 2.082.5-.. 12.2 4.0 24.5.- 12.2 6.0 30.5 12.3 0.5 39(2mln.) 12.1 1.0 54.5 5m1n.) 12.2 2.0 90.5 12.4 4.0 33.5-.- 12.0 0.0 21- 12.9

Above 350 ops.

mud. On the other hand, in some cases where only smallimpro'vement inviscosity is. desired, as little as 0.511). of the additive per barrelof mud will produce the desired efiect. Above about 4 lb. per barrel,the small increase in effect inmost cases would not warrant theadditional costof the material. 'The .use of larger These data show thatthe addition of the acrylic telomers in quantities upwards of 1 lb. .perbarrel effects a drastic reduction in viscosity of the mudwithontadversely affecting its thixotropic properties or its filtrationrate characteristics. In fact, the acrylic telomer additives tend toenhance these other properties as well.

EXAMPLE 7 I Since it is important that the drilling mud be stable atthe'bottom-hol'e temperatures encountered in drilling which sometimesreach as high as 250 F., the mud compositions of Example 6 weresubjected for 72ihorurs to a temperature of 300 F. and then retested bythe same procedures used originally. The data obtained are presented inTable VII.

Table VII Lb. Viscosity at Gel strength Filtration rate, Additiveadditive i 600-r.p m cc.v in 30 min. pH

per bbl. Stormer, All. cps. 0 Min. 10 Min.

Blank 0 10. 5 Telomer No. 1 0.6 Do 1.0 .10- 6 Above 350 cps.

These data convincingly demonstrate that these telomers Table X not onlysuffer no loss' in their efiectiveness as thinners V Amt. or ViscosityPercent but are afituauy more f il w mud whlch Type Mud Additive Addiat600r.p.m. Reducthey are incorporated 1s subrectedto elevated tempera Itive, Stormer, tionin tures. The ability to maintainreduced viscosityunder 5 cc. cps. Viscosity such severe temperature conditions is ahighly advantageous property not to be found. in most of thethinners ggg f gm g 223 i 8 of the prior art. do .1: 5 13s 60.9 do 10 41 88.3

Telomer N o. 2. 2 5 '0 s 8 ea-wa GIL EXAMPLE 8 Do 2 l 0 I Do 10 0 Do do90 Do Telomer N o. 2. 2 0 p Do do 10 0 A so-called gyp mud was preparedby adding to a 15 15 s2 clay suspension containing solids, 3.5 g. ofgypsum g g for each 350 cc. of the suspension and varying quantities Bof-the same acrylic telomers used in Example 6. The I g g? muds thusproduced were tested to evaluate the telomers 10 81 as thinners. Theresults of these tests are presented in 20 84 o 0 Table VIII. 1

2 40 5 64 Do do 10 71 Table VIII Lb; Viscosity Gel Strength- FiltrationAdditive Additive at 600r.p.m. ate, cc. pH

per bbl. V Stormer, m 30 Min.

cps. 0 Min. 10 Min. A. P. I.

Blank 0 Plastic 1 Plastic. 8, 5 TelomerNo. 1- 0.5 136 100 45.5 8.4 Do1.0 44 7.9 Do 2.0 35.5 7.6 Do 4.0 15.5 8.0 Do. 6.0 13 8.2 Telomer No. 2.0. 5 Plastic... 7 50 8. 8 Do 1.0 do 50.5 7.7 Do 2.0 70 33 7.7 Do 4.0 .12a 8.8 Do; 6.0 s 8.9

Above 350 cps. I Results here-are comparable with those in Example 6,indicating that the thinners of the invention are' not restricted to usewith lime-base muds but are also effective with gyp muds. A

EXAMPLE 9 The procedures carried out in Example 7 at 300 F. with thelime-base mud were repeated with the gyp mud of Example 8 containing thestated quantities of the telomers. Results are presented in Table IX.

' Fromthe foregoing it will be apparent that there has been provided bythis invention an additive which may be used for the purpose of reducingviscosity of drilling While the specific results obtained in thetreatment of various drilling fluids does. of course, vary somewhatdepending. upon the composition of the'fiuids, the thinner of theinvention is advantageously employed with drilling fluids containingclays of divergent characteristics. 50 Its beneficial effect onviscosity is obtained at little or no Table 1;:

/ Lb. Viscosity Gel Strength Filtration Additive Additive at 600r.p.m.Rate, cc. pH

per bbl. Stormer, m 30 Min.

cps. 0 Min. 10 Min. A. R.- I.

0 Plastic Plastic. Plastic. 6. 4 0.5 125 12 120 47.5 6.4 1. 0 .50 I 6. 52. 0 45 6. 8 4. 0 '23 7. 3 6. 0 15 7. 3 0. 5 44 6. 9 1. 0 6. 9 2. 0 377. 2 4. 0 8 7. 7 6.0 3. 5 8. 3

1 Above 350 cps. It is obvious from the above datathat the viscosity ofthe gyp mud treated with these-acrylic telomers is not significantlyaffected by subjection to elevated temperatures. 1 7

EXAMPLE 10 The viscosity reduced characteristics of the acrylic telomerswere also determined with muds other than those in which the sodiumcontent had been base exchanged with calcium. Table X shows the thinningeflfect of a 10% solution of the telomers described in Example 6 on a350 cc. sample of the mud indicated.

applications of the acrylic telomers as dispersants.

The preceding examples have illustrated two specific V weight.

11 Aqueous dispersions of other types of finely divided solid materialscan be prepared using the acrylic telomers. Aqueous dispersions ofadhesives, carbon black and cement are additional examples ofdispersions that can be prepared by incorporating therewith a minoramount of acrylic telomer.

telomer. As a specific example, a composition compris ing watercontaining 78% by weight of finely divided Portland cement was a plasticmass, too thick to be pumped with conventional equipment. When 0.29% byweight of solids of a sodium salt of a telomer of acrylic acid andcarbon tetrachloride, wherein the acid telomer had a molecular weight of1400, was incorporated there in, the composition became exceptionallyfluid, having a Fa-nn viscosity of only 60.5 cps.

The reaction products used in this invention are neither simple additionproducts nor interpolymers. Interpolymers result from a number ofmolecules of each reactant entering into the polymer chain and theproduct is ,a high molecular weight polymeric material. In the reactionproducts .of the invention, however, only one molecule of thehalogenated alkane compound'enters into the formation of each molecularspecies and the average molecular weight of the product is, in general,considerably lower than that of an interpolymer formed under comparableconditions. properties not to be found in the conventional acrylic acidpolymers of the prior art which make them particularly desirable incertain applications.

The following examples are presented to particularly illustrate a methodby which the acrylic telomers used in this invention can be prepared.All parts given are by EXAMPLE 11 A stainless steel rocking autoclave ofthree-liter capacity was charged with 222.4 parts of acrylonitrile,2577.6 palts of carbon tetrachloride and 3.3536 parts of benzoylperoxide. The autoclave was sealed, heated to 100 C. and rocked. at thattemperature for approximately five hours. At the end of that time, theautoclave was opened and its contents were filtered through a 'Buchnerfunnel. The precipitated polymer was dried at a tem peratureof 80 C. for36 hours to remove all traces of the chain transfer agent. The polymerproduct, a free flowing buff-colored powder of low bulk density, contained 25.2% N by Kjeldahl analysis, had a molecular weight of 1390,i.e., a degree of polymerization of approximately 26, and a specificviscosity of 0.2532 as determined at 30 C. on a solution of 0.2 g. ofthe material in 50 ml. of dimethylformamide. A yield of 190.0 parts ofthe telomer was obtained.

A 100-gram sample of the telomer was slurried with 750 ml. of distilledwater in a flask equipped with a stirrer, a thermometer and a refluxcondenser. A solution of 73 g. of sodium hydroxide (98%) in 250 ml. ofdistilled water was added to the slurry with stirring while the flaskwas heated gently. The mixture was not permitted to boil until most ofthe solid material had gone into solution. It was then kept under refluxconditions fora period of about 11.5 hours with provision being made toallow the water vapor to escape in order to concentrate the sample. Theresulting mixture of hydrolyzed telomer weighing 437.1 g. was analyzedand found=tocontain 51.4% H O (Fischer method) and only 0.9% residualnitrogen on a wet basis. The viscous solution was a clear dark ambercolor. The molecular weight of the hydrolyzed telomer thus obtained was1890 as calculated from the nitrile telomer from which it was derived.

Asecond sample of the same telomer was hydrolyzed by means of analcoholwater-caustic slurry technique in order that the hydrolyzedproduct might be recoveredin solid form by means of a simple filtrationstep. Approximately 47.1 g. (equivalent to 0.89 mole of acrylonitrile)Aqueous dispersions of cements are particularly improved byincorporating therewith acrylic These compositions, therefore, havespecial a of the telomer was charged with 200 g. of ethanol to athree-liter, triple-necked flask equipped with a stirrer, reflux.condenser and thermometer. The stoichiometric .quantity of sodiumhydroxide required for hydrolysis,

35.6 g. (0.89 mole) dissolved in 41.0 g. of distilled water was thenadded and the mixture was stirred thoroughly until the solid materialwas well wetted. Heat was applied to bring the mixture to boiling and itwas maintained under reflux conditions for about 14 hours. The mixturewas then filtered, the precipitate was washed several times withabsolute alcohol and dried overnight at 90 C. The yield of hydrolyzedtelomer was 83.1 g. or 98.6% of the theoretical and the productcontained 5.4% of residual nitrogen.

' EXAMPLE 12 A mixture of 278 parts of acrylonitrile, 3,222 parts of inot had .a molecular weight of 1100, representing anv av-.

erage degree of polymerization of about 18 or a structure correspondingto the formula The specific viscosity of'this telomer as determined at30 C. on a solution of 0.2 g. in ml. of dimethylformamide was 0.1671.

This telomer of acrylonitrile was hydrolyzed in an alcoholic causticslurry in a manner similar to that described in Example 11. About 600ml. of ethanol were placed in a 3-liter, triple-necked flask fitted witha thermometer, a reflux-condenser, and a stirrer with 120 g. (3 moles)of caustic dissolved in 135 g. of distilled water (7.5 moles) and 159 g.(equivalent to 3 moles of acrylonitrile) of the dried telomer was addedslowly with stirring. The exothermic heat of solution of the caustic inWater brought the temperature up to about -60 C. and the mixture wasthoroughly stirred for about 20 minutesbefore any heat was applied. Thenthe temperature was brought up to boiling by means of a heating mantleand the whole was refluxed for a period of about 9 hrs. A portion of thealcohol was removed by distillation at an overhead temperature of 782 C.The mixture was filtered, the

precipitate was washed with the distilled alcohol, and

. dried in an oven at C. The yield of hydrolyzed product containing4.55% of residual nitrogen and having a molecular weight ofapproximately 1642 was 27.3 g., or 96%.

EXAMPLE 13 alcoholic medium, in this case isopropanol being employed,the acrylonitrile telomer is converted to an acrylic telomer having amolecular weight and properties very similar to those obtained in theother examples given above.

Many variations in procedure from thosegiven in the examples both in themanner of preparation of the acrylic telomers and in the hydrolysis ofthem may be made. For

example, "of the halogenatedgalkanesfsuch-as 2 4 12, 2 3 ls zHs Iza 3 62: fi si cHsF, CH I, CH I ,"CI;, .CBr CHBr CH Br CH Cl, etc., are assuitable as telogens as are 'the carbon tetrachloride anddichloromethane mentioned.

The mole ratio of the halogen'ated alkane to the nitrile may vary overthe range from 1:1 to 10:1, for example, depending upon the molecularweight desired in' the product. Generally, the molecular weight of thetelomer formed decreases with an increase in the ratio of thehalogenated alkane or chain transfer agent, to nitrile employed. Sincethe preferred molecular ratio will depend upon thev desired chainlengt-hof the product, considerable latitude 'ma y he exercised in the choiceof reactant quantities. with regard to the excessl oflchain transferagent used. Amounts greater than thafrepresented by the 10:1 ratio,while they maybe employed, serve no usefulpurpose and necessitaterecovery" of an excess quantity of the chlorinated transfer. agent foreconomical reasons.

' Catalysts orinitiators .of, polymerization other than the benzoylperoxide and tertiarybutyl hydroperoxide mentioned may also be .used.,Generally, suitable materials for catalyzing the present process arefree-radicalliberating agents, i.e., compounds which will decompose togive free radicals. Such compounds include peroxygentype catalysts, for,example, acyl peroxides such as acetyl, benzoyl, .lauroyl or ,stearoylperoxides; hydrocarbon peroxides jor hydroperoxides such asdi-tert-aimyl peroxide, -tert butyl t; ;hyd'roperoxide cjumenehydroperox-ide, 1p -.cymene hydroperoxide, and inorganic. :percompoundssuch as hydrogen peroxide,sodium peroxide, sodium perborate, -potas$i11,,1-;persu1f ate, and'alkali percarbonates; hydrazine derivatives ;:suchas hydrazine hydrochloride and dibenzoyl hydrazine; organometalliccompounds such as tetraethyllead and the like. The quantity of catalystuseful for promoting the addition reaction may range from as little as0.5% to as much as 5% by weight of the nitrile reacted. Usually, optimumyields are obtained withamounts, ofcatalyst representing from 23% bywleightof the nitrile employed. 1 ;}Quantities of more than""5% serve no'useful'ipurposeam may even cause detrimental sidereactionsjhencejshould not be used.

Ultraviolet light may be employed with the catalyst or as the solecatalytic'ag'ent.

Neither reaction time nor reaction temperature is critical. The, timeduring which the nitrile and halogenated alkanefarereactedm'aybewidely'varied depending upon the reactant quantities, the reactiontemperature used, the nature of the individual catalyst employed, etc."Generally, times of from one to twentyfour hours are employed. Thetelomerization reaction may be carried out over a wide range oftemperatures from 50 C. to 150 C. or above. The preferred temperaturedepends primarily on the catalyst employed since the minimum temperatureof the reaction is that required to decompose the catalyst and generatefree radicals. When benzoyl peroxide is the catalyst, for example, thereaction is usually initiated at about 60 C. to about 100 C. while withdi tertiary butyl peroxide, reaction begins at about 100 C. to about 120C. Optimum yields are generally obtained by operatingat temperatureswhich permit steady decomposition of the catalyst, with consequentsteady liberation of free radicals.

Conditions under which hydrolysis is effected may likewise be varied tosome extent. Depending upon the product desired, for example, hydrolysismay be effected by means of either an acid or a base. Suitable acids aresulfuric acid and hydrochloric acid; while the alkali metal hydroxidessuch as sodium and potassium hydroxide and ammonium hydroxide, aresuitable bases for the hydrolysis reaction. In acid hydrolysis, thecyanide, or CN, groups in the telomer are converted into either amide,CONH or carboxyl, COOH, groups according to the extent of thehydrolysis, the amount of Water employed There-is, however, a limitingfactor being the main controlling factor. Complete hydrolysis yields theacid derivative, while the intermediate hydrolysis product is the amide.On the other hand, hydrolysis in the presence of a base yields a productwherein the nitrile group has been converted to the acid salt such asCOONa, COONH etc.

Generally, for complete hydrolysis, for each molecular part of telomerthere is employed a molecular part of acid or base and two molecularparts of water. In hydrolyzing to the amide stage, however, only one.mole of water and one mole of acid is required per mole of telomer. Forpractical purposes and to insure as complete hydrolysis as possible,water is usually employed in'slight excess, for example, 2.5 moles permole of telomer.

The hydrolyzing reaction occurs to a minor extent at room temperaturebut generally the application of some heat is required. Temperaturesbelow 100 C. are employed with temperatures usually maintained at fromabout 40 to about -80 C. Preferred temperatures lie in the range fromabout 60 to about 70 C. The time required for the reaction varies withthe temperature of the-reactionbeing and longer fora lower temperature.within the preferred temperature range,

six hours is satisfactory, while a time from about three to aboutfour'hours is preferred. Extended periods of time in excess of thosementioned result in little-variation in theresidual' nitrog'en contentof the finished ac'rylic However, recovery is complicated 'by the factthat such large amounts of water must be evaporated since thetelomcrs'are produced in such dilute solutions. viate these problems,therefore, hydrolysis may be carried out in'a medium which isnon-solvent for both the acrylonitrile telomer itself and the hydrolyzedor acrylic telomer but which is miscible with water and the acid or;base used. Many alcohols are useful for this pur- In decreasing order oftheir utility, there may To obpose. be mentioned, for example, ethanol,isopropanol or propanol, methanol, and ethylene glycol.

Depending upon the hydrolysis conditions employed, any and all of thefollowing species of acrylic telomers as well as others not listed maybe produced by hydrolysis of the corresponding acrylonitrile telomers, nin each case being an integer from 2 to 30.

shorter for a higher temperature ,When operating it has been shown thata reaction time between about 0.5 hour and about CHzOl I, .OI OH C ONait 'What is claimed is:

'1..A drilling fluid comprising an aqueous suspension of:cla-ycontaining a telomer of a monomeric material selected from thegroup consisting of acrylic acid, its alkali metaljand ammonium saltsand acrylamide, anda halogenated'alkanetsaid telomers containing themonomcric unit having the formula Clix-CH l at wherein iY-is selectedfrom the group consisting of H,,

NH; andOM, M "being a cationselected from the group consist-ingof thealkali metals and ammonium andn is an ,integer'from 2 to '30, saidtelomer being present in an amount suificient to preventflocculationofsaid finely; divided solid material.. 7

t2. A'drilling fluid comprising an aqueous suspension of clay containinga telomer of a monomeric material selectedfrom the group consisting ofacrylic acid, its alkali metal and ammonium ,salts an d acrylamide, anda halomethane, (said telomers containing the monomeric unit having theformula 1 Lenten-J; t r l i Y n whereinY is selected from .the groupconsisting of OH, NH and 0M, M being a cation selected from the groupconsisting of the alkali metals and ammonium and n is an integer from '2to 30, said telomer being present in an amount sufficient to-preventflocculation ofjsaid finely divided solidmaterial. g q '3. A drillinglfluid comprising an aqueous suspension of clay containing atelomerhaving the formula where X is selected from the group consistingof hydrogen and halogen, Y is selected from the group con sisting of NHOH and OM, M being a cation selected from the group consisting of thealkali metals and ammonium, 'Z is a halogen, n is an integer from 2 to30 and in may vary from 0 to 2 inclusive, said telomer being present inan amount suflicient to prevent flocculation of said finely dividedsolid material.

4. A drilling fluid comprising an aqueous suspension of clay containinga telomer having the formula wherein Y is selected from the groupconsisting of OH, NH and OM, M being a cation selected from the groupconsisting of the alkali'metals and ammonium and n is an integer from 2to 30, said telomer being present in an .amount sufiicient to preventflocculation of said finely'divided solid material.

*5. A drilling fiuidas described in claim 4 wherein Y is OM and M ischosen frorn the group'consisting of the alkali metals and ammonium.

'6. A drilling fluid as described in claim 5 wherein M is sodium. 1 f

7. Adrilling fluid comprising an aqueous suspension of clay containing atelomer of the formula wherein Y is selected from the group consistingof 0H, NH and OM, M being a cation selected from the group consisting ofthe alkali metals and ammonium and n is an integer from 2 to 30, 'saidtelomer being present in an amount sufiicient to prevent flocculation ofsaid'finely divided solid material.

' References Cited in the file of this patent I UNITED STATES PATENTS2,398,426

Hanford w Apr. 16, 1946 2,552,775 Fischer et al. May 15, 1951 2,718,497Oldham et a1. Sept. 20, 1955 2,727,835 Barrett Dec. 20, 1955

1. A DRILLING FLUID COMPRISING AN AQUEOUS SUSPENSION OF CLAY CONTAININGA TELOMER OF A MONOMERIC MATERIAL SELECTED FROM THE GROUP CONSISTING OFACRYLIC ACID, ITS ALKALI METAL AND AMMONIUM SALTS AND ACRYLAMIDE, AND AHALOGENATED ALKANE, SAID TELOMERS CONTAINING THE MONOMERIC UNIT HAVINGTHE FORMULA